The present invention relates generally to films and composite articles for paint replacement and methods related to the same.
Painted surfaces are commonly used in many different types of applications. Painted surfaces can not only improve aesthetic properties of a surface, but they can also improve functional properties of underlying surfaces and help protect the same. One such application is in the transportation industry, where exterior painted surfaces are typically exposed to a variety of environments, some of which can be very harsh on the surface. Examples of articles in the transportation industry having such painted surfaces include vehicles providing transportation over land, in the water, and in the air. Such vehicles include aircraft and motorized vehicles like automobiles and trucks. The paint on such surfaces can function to protect the underlying surface from damage due to that exposure. However, the paint itself must also be durable to withstand repeated exposure to such damaging environments.
Painting exterior surfaces on vehicles poses many challenges, not only due to the amount of surface area typically requiring painting and the often uneven topography of such surfaces, but also due to increasingly stringent environmental regulations. For example, there is a desire for and increasingly regulations requiring a reduction in Volatile Organic Component (VOC) emissions, particularly in industries utilizing significant amounts of paint and other organic chemicals. VOC emission reduction and water conservation, both associated with conventional painting processes, are therefore increasingly important environmental considerations.
A further consideration associated with painting exterior surfaces on vehicles, particularly in the transportation industry, is overall weight. The presence of paint on a surface, while increasing the aesthetic and functional properties of the surface, also increases the weight of the article to which it is applied. In the transportation industry, additional weight leads to consumption of excess fuel and restrictions on the number of passengers or amount of cargo that an associated vehicle can safely and efficiently transport.
Further, a unique consideration associated with painting or otherwise covering exterior surfaces on aircraft and similar vehicles is the impact of the relatively high vehicle speeds on the surface of the vehicle and any coatings or coverings thereon. For example, wind resistance associated with travel at high speeds can make it difficult to retain uniform and adequate adherence of such coatings or coverings on a vehicle's surface. Thus, coatings and coverings developed for application to exterior surfaces of vehicles traveling on, for example, land are often not adequate to withstand the challenging conditions associated with higher speeds of travel through air.
To overcome many of the challenges associated with painting exterior surfaces of vehicles using conventional methodology, a number of paint replacement technologies have been developed so that use of paint can be minimized or avoided. For example, by infusing plastic with pigment, one commercially available product allows car manufacturers to remove the painting process from automobile production lines. Such a product, which comprises a resin for formation of surfaces that are traditionally painted, is marketed under the LEXAN SLX trade designation by General Electric Company of Fairfield, Conn. It is advertised that one can now achieve a high-gloss, sun- and scratch-resistant finish without the need for paint when using such a resin.
Other alternatives to using conventional paint include adherence of a paint replacement film or sheet to a surface. For example, 3M Company of St. Paul, Minn. markets paint replacement films and tapes. It is advertised that such films were created while developing top-coat paint replacement technology for use on the demanding exterior surfaces of aircraft. Further, it is advertised that such films couple the low surface energy performance of fluoropolymer films with a range of self stick and curing adhesives. See also U.S. Patent Publication No. 2007/0047099 and U.S. Pat. No. 7,141,303, both of which are assigned to 3M Innovative Properties Company.
U.S. Pat. No. 5,965,256, also assigned to 3M Innovative Properties Company, describes protective and decorative film-based coatings for surfaces exposed to adverse environments, including outdoor weather, solvents, dirt, grease, marine environments, and the like. One film exemplified therein is described as an aircraft paint replacement film. Such films include interpenetrating polymer networks, described as preferably acrylate-urethane interpenetrating polymer networks (IPN). They may optionally have a layer of a highly fluorinated polymer at the outermost, exposed surface. The substrate on which the films are adhered can be a cured adhesive, preferably a cured pressure-sensitive adhesive (PSA), in which case the fluoro-containing polymer layer is said to typically be situated between the PSA layer and the IPN layer. Alternatively, the substrate can be a surface to be protected from exposure to weather, chemical exposure, graffiti, or the like on, for example, a vehicle such as an automobile, a truck, a boat, or an aircraft; an outdoor sign; or a building's exterior.
U.S. Pat. No. 6,475,616, also assigned to 3M Innovative Properties Company, describes paint replacement appliquës comprising: a backing comprising a fluorinated polymer having two treated surfaces, an adhesive layer on one treated surface and a cured urethane coating layer on the other treated surface. The cured urethane coating layers on the appliquës are made from the reaction products of a hydroxy-containing material (base material) and isocyanate-containing material (activator). The curable compositions having the hydroxy- and isocyanate-containing materials may also further comprise a colorant. The curable compositions usually contain solvents and may also further contain other additives such as UV-stabilizers, antioxidants, corrosion inhibitors, curing catalysts, and the like. It is stated that, when dried and cured, the urethane coating layer provides a conformable urethane coating layer that has improved gloss retention and gouge and scratch resistance as compared to, for example, a fluoropolymer layer alone.
However, these 3M films have not proven reliable in maintaining their integrity and adherence to the underlying surface when exposed to the environment under expected operating conditions. A contributor to this undesirable quality is the nature of bonding between the film and underlying surface (i.e., bonds relying on Van Der Waals forces, such as those typically associated with use of pressure sensitive adhesives, as opposed to stronger bonds, such as covalent bonds). Further, it is believed that inclusion of fluoropolymer layers in such films contributes to interlayer delamination due to its low surface energy and inadequate bonding to adjacent layers. Still further, if additional coatings or coverings are desired to be applied to the exterior surface of such films, the low surface energy fluoropolymer films therein make it challenging to find a coating or covering that will adequately adhere thereto.
3M Company also markets films for application over painted surfaces that are intended to help maintain the beauty and integrity of such surfaces. These films are marketed under the SCOTCHGARD PAINT PROTECTION FILM trade designation. The urethane films are described as being useful on vulnerable exterior painted surfaces such as leading hood edges, fender end caps and rocker panels to protect against stone chips, bug damage, abrasion and weathering. The film is advertised as being transparent and nearly invisible, such that it does not alter a vehicle's appearance.
U.S. Pat. No. 7,141,294, assigned to 3M Innovative Properties Co. describes a decorative film using no appreciable amount, or no amount, of polyvinyl chloride. This decorative film comprises a substrate, an adhesive layer for sticking the decorative film to an adherend formed on one surface of the substrate, a printed layer provided with a printed decorative pattern or character information formed on the other surface of the substrate, and a top clear layer for protecting the printed layer. The substrate is formed from an ethylene-(meth)acrylic acid copolymer. The top clear layer used as an outer-most layer is preferably made of a material which is superior in weatherability and water resistance and has high transparency (e.g., colorless coating compositions such as fluororesins, thermosetting urethanes, and ultraviolet-curing compositions). The decorative film is described as having flexibility for adhering, ink adhesion, water resistance, and weatherability with good balance. It is also described as being suitable for various adherends, particularly for adhering to buildings or vehicles used outdoors, including curved surfaces such as the body of vehicles.
U.S. Pat. No. 5,034,275 refers to a paint-coated sheet material. The material purportedly comprises a flexible and stretchable thermoplastic polyester carrier film, a stretchable aqueous polyurethane paint layer, a stretchable transparent crosslinked polyurethane topcoat layer and, disposed between the carrier film and the paint layer, a thin tie layer formed by coating an aqueous dispersion of a neutralized copolymer of ethylene and an ethylenically unsaturated carboxylic acid on the carrier film. The thickness of the crosslinked polyurethane topcoat layer is stated to be substantially thicker than the paint layer, which is stated to have a thickness of 12 to 80 microns. In that regard, the topcoat layer has a thickness in the range of about 0.02 to 0.25 millimeter (20 microns to 250 microns), preferably from about 0.03 (30 microns) to 0.1 millimeter (100 microns).
U.S. Pat. No. 5,114,789 describes a decorative sheet material having a transparent topcoat that can be bonded to various substrates, such as exterior automotive panels, as a protective and decorative coating. The sheet material comprises a thin carrier film, a paint layer adhered to one surface of the carrier film, and a crosslinked topcoat layer. That topcoat layer is stated to be “extremely thick”—at least 0.1 millimeter (100 microns)—in embodiments described therein.
U.S. Pat. No. 5,242,751 describes a paint composite article including a thermally deformable carrier film having, on its first major surface, an adhesive layer and, on its second major surface, a paint layer consisting of a pigmented basecoat covered by a polyurethane topcoat layer.
U.S. Pat. No. 5,268,215 describes a paint-coated film purportedly having good mar resistance. A polyurethane paint layer is coated on a polymeric carrier film. Coated on the upper surface of the paint layer is a polyurethane clearcoat layer, which is then coated with a polyurethane-siloxane topcoat layer. The film can purportedly be thermoformed, stretched, and bonded adhesively to auto body parts, boats, household appliances, and other substrates as protective and decorative coverings having a basecoat-clearcoat appearance.
U.S. Pat. No. 5,468,532 describes a multi-layer graphic article with a color layer. It is based on a polymeric film that is covered with a protective surface layer to purportedly make the article weatherable and resistant to chemical exposure. The protective surface layer is described as being a polyurethane-based material in an exemplary embodiment.
U.S. Pat. No. 6,132,864 describes a painted plastic film, which is coated with two or more coats of certain materials. It consists of a base plastic film, which is first coated with a filler composition, followed by coating with a pigmented paint, and then coating with a transparent plastic film. The base plastic film can be a polyolefin, a polyamide, a polyurethane, a polyester, a polyacrylate, a polycarbonate or mixture of different polymeric substances. The filler composition is described as a composition containing a binder and crosslinking agent among other components. The pigmented paint coating is described as a topcoat comprising a polymeric binder, with or without a crosslinking agent, and a pigment or mixture of pigments. The transparent plastic film is described as being one of the same materials suitable for use as the base film. The multi-layer sheets described therein purportedly have good resistance to stone chipping and corrosion.
Despite the number of paint replacement technologies, conventional technology has not satisfactorily addressed paint replacement in all situations, particularly applications involving vehicles used for air transportation. Not only are adequate adhesion and durability issues for exterior surfaces on such vehicles due to their typical exposure to high wind resistance, but other issues exist as well. For example, many aircraft and other transportation vehicles increasingly rely on use of composite materials for surfaces to which conventional paint replacement materials are adhered. Conventional paint replacement materials, however, often do not adhere as well to composite materials as they do to individual materials.
It is known that the ability of conventional paint replacement materials to adhere adequately to all surfaces, including those formed from composite materials, and provide the desired aesthetic and functional properties is often inadequate. Not only is it desirable for a material to adhere adequately to a surface, but it is also desirable to be able to remove the material easily when desired. In the case of an aircraft, for example, company logos and designs often change, which leads to a desire to refinish aircraft displaying outdated logos and designs. This is particularly prevalent in the case of leased aircraft, which often undergo multiple and repeated changes of possession and, thus, changes in associated individual or company logos and designs. Typically paint replacement films present on a surface must first be removed when refinishing the surface. Many conventional films, however, are not easily removable as the layers therein are prone to delamination. Delamination of the paint replacement film when removing the same from a surface can significantly complicate the refinishing process.
Even when paint, as opposed to a paint replacement film, is present on a surface to be refinished, the refinishing process can be problematic. Refinishing painted surfaces typically entails sanding the surface in preparation for applying a fresh coat of paint thereon. Composite material surfaces must usually rely on sanding to remove undesired paint thereon when refinishing because most chemical strippers are not able to be used on composite materials. Sanding surfaces formed from composite materials, however, is also not desirable due to the likelihood that such sanding will result in damage to (e.g., breakage of) the composite's reinforcement material (especially when that reinforcement material comprises fibers).
As noted, a number of problems are inadequately addressed by conventional paint replacement technologies. Thus, alternative paint replacement technologies are desired.